1. Field of the Invention
The present invention relates to a resin sealing method and apparatus for a semiconductor device. More particularly, the invention relates to a resin sealing method and apparatus which are well adaptable for the resin sealing of a semiconductor device having an underfill structure, e.g., a semiconductor device including a flip-chip connected semiconductor chip.
2. Description of the Related Art
A semiconductor device having a semiconductor chip mounted by a flip chip method is shown in FIG. 16. As shown, a semiconductor chip 12 is flip-chip connected onto a substrate 10, and then a joining portion between the semiconductor chip 12 and the substrate 10 is filled with sealing resin 14, to thereby seal the joining portion by resin. The sealing resin 14 functions to protect the joining portion between the semiconductor chip 12 and the substrate 10 and to relieve a thermal stress caused by the thermal coefficient difference of expansion between the substrate 10 and the semiconductor chip 12.
A known method of filling the joining portion with resin 14, generally used, is shown in FIG. 17. As shown, the substrate 10 is slantly supported, and in this state, sealing resin 14 is allowed to flow into the joining portion between the substrate 10 and the semiconductor chip 12. A number of solder bumps 16 are studded on the joining portion between the substrate 10 and the semiconductor chip 12. The sealing resin 14 flows through gaps among those bumps 16. To make the flow of the sealing resin easy, the substrate 10 is slanted, and the sealing resin 14 flows onto the slanted substrate 10 while expelling air from the joining portion.
When the sealing resin 14 is allowed to merely flow into the joining portion of the flip-chip connected semiconductor chip 12 to fill out there, the sealing resin 14 imperfectly fills the joining portion between the semiconductor chip 12, and sometimes the substrate 10 and air bubbles are left in the gap portion. Actually, the width of the joining portion (between the semiconductor chip 12 and the substrate 10) is about 0.1 mm, and recently it is reduced from 0.1 mm to 0.02 mm to 0.03 mm, extremely narrow. A number of solder bumps 16 are studded in the joining portion, and those bumps restrict the flow of the sealing resin 14. When the filler-contained resin is used, the resin flow is further impeded. Therefore, the method of merely flowing the sealing resin 14 into the underfilled portion cannot achieve the reliable sealing. A resin hardening time in the potting process is longer than in the transfer molding process. Therefore, also in the work efficiency, the method by merely flowing the sealing resin 14 into the underfilled portion is not preferable.
The solder bumps are minutely different in height and the semiconductor chips are also minutely different in thickness with the pieces to be molded. Therefore, when the transfer molding is used for sealing flip-chip connected semiconductor chip by resin, the following disadvantages are present: 1) a thin layer of resin will be formed on the outer surface of the semiconductor chip; and 2) the resin excessively presses the molded piece to possibly break the molded piece. Further, the resin material including extremely small silica particles or not including the same must be used since the gaps in the underfilled portion are extremely small. Such a resin material is easy to enter the gaps. Therefore, if the clamping of the molded piece is not properly, the resin will enter the gaps to form resin flash. The same disadvantageous phenomenon occurs also when the semiconductor chip is minutely displaced (when viewed in plan) on the substrate. For this reason, it is almost impossible to resin seal the underfilled portion resulting from the flip-chip connection by the conventional transfer molding process.